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authorRafael J. Wysocki <rafael.j.wysocki@intel.com>2014-05-16 02:46:50 +0200
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2014-05-16 23:15:44 +0200
commitaae4518b3124b29f8dc81c829c704fd2df72e98b (patch)
tree6ab2d44ce8282838d33450e0895e8ca88ac0abcf /drivers/base
parentf6514be5fe7fe796041b673bad769510414ff2b9 (diff)
PM / sleep: Mechanism to avoid resuming runtime-suspended devices unnecessarily
Currently, some subsystems (e.g. PCI and the ACPI PM domain) have to resume all runtime-suspended devices during system suspend, mostly because those devices may need to be reprogrammed due to different wakeup settings for system sleep and for runtime PM. For some devices, though, it's OK to remain in runtime suspend throughout a complete system suspend/resume cycle (if the device was in runtime suspend at the start of the cycle). We would like to do this whenever possible, to avoid the overhead of extra power-up and power-down events. However, problems may arise because the device's descendants may require it to be at full power at various points during the cycle. Therefore the most straightforward way to do this safely is if the device and all its descendants can remain runtime suspended until the complete stage of system resume. To this end, introduce a new device PM flag, power.direct_complete and modify the PM core to use that flag as follows. If the ->prepare() callback of a device returns a positive number, the PM core will regard that as an indication that it may leave the device runtime-suspended. It will then check if the system power transition in progress is a suspend (and not hibernation in particular) and if the device is, indeed, runtime-suspended. In that case, the PM core will set the device's power.direct_complete flag. Otherwise it will clear power.direct_complete for the device and it also will later clear it for the device's parent (if there's one). Next, the PM core will not invoke the ->suspend() ->suspend_late(), ->suspend_irq(), ->resume_irq(), ->resume_early(), or ->resume() callbacks for all devices having power.direct_complete set. It will invoke their ->complete() callbacks, however, and those callbacks are then responsible for resuming the devices as appropriate, if necessary. For example, in some cases they may need to queue up runtime resume requests for the devices using pm_request_resume(). Changelog partly based on an Alan Stern's description of the idea (http://marc.info/?l=linux-pm&m=139940466625569&w=2). Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Acked-by: Alan Stern <stern@rowland.harvard.edu>
Diffstat (limited to 'drivers/base')
-rw-r--r--drivers/base/power/main.c66
1 files changed, 51 insertions, 15 deletions
diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
index 86d5e4fb5b9..343ffad5937 100644
--- a/drivers/base/power/main.c
+++ b/drivers/base/power/main.c
@@ -479,7 +479,7 @@ static int device_resume_noirq(struct device *dev, pm_message_t state, bool asyn
TRACE_DEVICE(dev);
TRACE_RESUME(0);
- if (dev->power.syscore)
+ if (dev->power.syscore || dev->power.direct_complete)
goto Out;
if (!dev->power.is_noirq_suspended)
@@ -605,7 +605,7 @@ static int device_resume_early(struct device *dev, pm_message_t state, bool asyn
TRACE_DEVICE(dev);
TRACE_RESUME(0);
- if (dev->power.syscore)
+ if (dev->power.syscore || dev->power.direct_complete)
goto Out;
if (!dev->power.is_late_suspended)
@@ -735,6 +735,12 @@ static int device_resume(struct device *dev, pm_message_t state, bool async)
if (dev->power.syscore)
goto Complete;
+ if (dev->power.direct_complete) {
+ /* Match the pm_runtime_disable() in __device_suspend(). */
+ pm_runtime_enable(dev);
+ goto Complete;
+ }
+
dpm_wait(dev->parent, async);
dpm_watchdog_set(&wd, dev);
device_lock(dev);
@@ -1007,7 +1013,7 @@ static int __device_suspend_noirq(struct device *dev, pm_message_t state, bool a
goto Complete;
}
- if (dev->power.syscore)
+ if (dev->power.syscore || dev->power.direct_complete)
goto Complete;
dpm_wait_for_children(dev, async);
@@ -1146,7 +1152,7 @@ static int __device_suspend_late(struct device *dev, pm_message_t state, bool as
goto Complete;
}
- if (dev->power.syscore)
+ if (dev->power.syscore || dev->power.direct_complete)
goto Complete;
dpm_wait_for_children(dev, async);
@@ -1332,6 +1338,17 @@ static int __device_suspend(struct device *dev, pm_message_t state, bool async)
if (dev->power.syscore)
goto Complete;
+ if (dev->power.direct_complete) {
+ if (pm_runtime_status_suspended(dev)) {
+ pm_runtime_disable(dev);
+ if (pm_runtime_suspended_if_enabled(dev))
+ goto Complete;
+
+ pm_runtime_enable(dev);
+ }
+ dev->power.direct_complete = false;
+ }
+
dpm_watchdog_set(&wd, dev);
device_lock(dev);
@@ -1382,10 +1399,19 @@ static int __device_suspend(struct device *dev, pm_message_t state, bool async)
End:
if (!error) {
+ struct device *parent = dev->parent;
+
dev->power.is_suspended = true;
- if (dev->power.wakeup_path
- && dev->parent && !dev->parent->power.ignore_children)
- dev->parent->power.wakeup_path = true;
+ if (parent) {
+ spin_lock_irq(&parent->power.lock);
+
+ dev->parent->power.direct_complete = false;
+ if (dev->power.wakeup_path
+ && !dev->parent->power.ignore_children)
+ dev->parent->power.wakeup_path = true;
+
+ spin_unlock_irq(&parent->power.lock);
+ }
}
device_unlock(dev);
@@ -1487,7 +1513,7 @@ static int device_prepare(struct device *dev, pm_message_t state)
{
int (*callback)(struct device *) = NULL;
char *info = NULL;
- int error = 0;
+ int ret = 0;
if (dev->power.syscore)
return 0;
@@ -1523,17 +1549,27 @@ static int device_prepare(struct device *dev, pm_message_t state)
callback = dev->driver->pm->prepare;
}
- if (callback) {
- error = callback(dev);
- suspend_report_result(callback, error);
- }
+ if (callback)
+ ret = callback(dev);
device_unlock(dev);
- if (error)
+ if (ret < 0) {
+ suspend_report_result(callback, ret);
pm_runtime_put(dev);
-
- return error;
+ return ret;
+ }
+ /*
+ * A positive return value from ->prepare() means "this device appears
+ * to be runtime-suspended and its state is fine, so if it really is
+ * runtime-suspended, you can leave it in that state provided that you
+ * will do the same thing with all of its descendants". This only
+ * applies to suspend transitions, however.
+ */
+ spin_lock_irq(&dev->power.lock);
+ dev->power.direct_complete = ret > 0 && state.event == PM_EVENT_SUSPEND;
+ spin_unlock_irq(&dev->power.lock);
+ return 0;
}
/**